1. Field of the Invention
The present invention relates to an ink absorbing body to which ink is injected, an ink tank incorporating the ink absorbing body and being used for supplying a liquid through a supply opening as required, and a production method of the ink tank. The invention further relates to an ink-jet cartridge including an ink-jet printing head and an ink-jet printing apparatus.
2. Description of the Related Art
In an ink tank to be used in an ink-jet printing apparatus, the ink tank including an ink tank portion in a form of an ink-jet cartridge integrally incorporating a printing head, it is typical to provide means for adjusting a pressure of an ink stored in the ink tank to be negative pressure relative to the atmospheric pressure so as to obtain good ink supplying ability for an ink-jet printing head as printing means.
As generation means of such pressure, hereinafter referred to as "vacuum", an ink absorbing body formed of a polyurethane foam is frequently employed. It is the trend in the recent years to employ a method utilizing a fiber including a fiber bundle having directionality, felt or so forth.
For example, Japanese Patent Application Laid-open Nos. 15839/1994 and 255121/1994 disclose employment of an ink holding body formed of felt, respectively. Also, commonly owned Japanese Patent Application Laid-open No. 20115/1996 proposes an ink tank having a region of filling fibrous body at least at an ink supply side, wherein the fibrous body is deformed within a range of elastic bending, and wherein the fibrous body is filled within the region at the state of forming a plurality of intersections in various directions within the region.
On the other hand, considering the ink to be injected into the ink absorbing bodies above, there have been developed inks satisfying requirement for clearer color output on a plain paper, improvement of water resistance in a post card when ink is discharged on the surface of the post card, and so forth, in the recent years.
For example, in order to suppress bleeding at boundary region between the different color regions, which are adjacent to each other, upon color printing on the plain paper, it has been performed to discharge or eject a pre-treatment liquid at predetermined printing position on the printing paper in advance of ejection of the ink, and subsequently to eject a super-penetration type ink containing anionic dye to cause reaction with the pre-treatment liquid for making the dye insoluble. When measure for the foregoing requirement is taken by improving the ink, it has been required to define optimal physical property with respect to components contained in the ink.
The fiber to be used as the ink absorbing body has superior property in ink absorbing efficiency and chemical stability in contacting with the ink, in comparison with the method utilizing foamed body, such as polyurethane foam or so forth as the ink absorbing body, in the prior art. This is because the actual volume of the fibrous ink absorbing body in the internal volume of the ink tank is smaller than that of the conventional ink absorbing body of the foamed body, and because the fiber per se is not reactive to the ink.
Particularly, when polyolefin resin which is inexpensive and has superior acid resistance, alkalescence resistance and solvent resistance, is taken as material for the fiber, the fiber may have superior chemical stability relative to the ink. Therefore, the ink absorbing body has been designed under the premise of inert property relative to the ink.
However, the present inventors have found, as results of study, when the ink including an anionic dye is stored in the ink and stored for a long period at a temperature of 60.degree. C., it has been found that significant variation of printing quality is possibly caused. Upon checking of physical property value of the ink, it has been found that the ink has higher viscosity and lower surface tension in comparison with initial physical property of the ink.
On the other hand, when the ink absorbing body is washed with pure water before injection of the ink, and the ink absorbing body absorbing the ink is stored for a long period under the same condition, difference of the printing quality can be seen in comparison with the case where washing of the absorbing body is not performed.
Through such experiments, the present inventors had obtained a conclusion that a substance which may cause physical property of the ink is deposited on the ink absorbing body, and, getting one step ahead, obtained a novel idea which could not be through of in the prior art. The idea is that, by positively utilizing the foregoing property of the substance, an optimal performance is provided for the ink absorbing body to be used with the ink tank for an ink-jet, which is optimal for ink injection before injecting of the ink and staple with respect to the ink after injection of the ink.
In viewpoint of such novel idea, production process of the ink absorbing body including the production process of the fiber as the elemental material, has been reviewed again. As a result, irrespective of the form of the fiber to be used, such as felt, fiber bundle or so forth, attention has been attracted to an oily material to be deposited on the fiber. As the oily material, a kind of oily material corresponding to application of the fiber is used. The depositing amount of the oily material on the fiber is in a ratio range of 0.5 wt % to 2 wt % with respect to the fiber weight, in the weight after drying. The oily material contains the surfactant in chemical composition.